Liquid dispenser for dispensing foam

ABSTRACT

A pump assembly provides for direct replacement of volumes of liquid from a reservoir with equal volumes of air preferably at substantially atmospheric pressure, the same pressure or with pressure equalization to be at least equal to atmospheric pressure. A slide arrangement preferably positively displaces liquid from the reservoir and air into the reservoir. The pump draws air from the atmosphere into a chamber from which the air either is available for passage to replace liquid from the reservoir or is pressurized to assist dispensing liquid, preferably, admixing with the liquid to provide foaming. Gravity separation of air and liquid to be dispensed is used to replace liquid with air in the reservoir and to selectively place air and liquid into communication with passageways for ejection.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 09/965,821, filed Oct. 1, 2001 and issued as U.S. Pat. No.6,409,050 on Jun. 25, 2002.

SCOPE OF THE INVENTION

This invention relates to liquid dispensers and, more particularly,liquid dispensers to dispensing liquid as a foam.

BACKGROUND OF THE INVENTION

Liquid dispensers for dispensing soaps and other similar fluids inliquid form are known. For various reasons in some applications, it ispreferable to dispense soaps and other similar fluids in the form of afoam. Generally, in the form of a foam, less soap liquid is required tobe used as contrasted with the soap in the liquid form. As well, soap asfoam is less likely to run off a user's hands or other surfaces to becleaned.

Known liquid dispensers for dispensing foams include the dispensertaught by U.S. Pat. No. 5,445,288 to Banks, issued Jul. 29, 1995. Adisadvantage which the present inventor has appreciated with dispenserssuch as those taught by Banks is that when used with a non-collapsibleor rigid sealed container of soap liquid, a vacuum comes to be developedin the container which renders the dispenser inoperative.

Known liquid dispensers for dispensing liquids without foaming of theliquids are also known. The present inventor has also appreciated thatmany such dispensers also suffer the disadvantage that they are notsuitable for use with non-collapsible or rigid sealed containers sincethe pumps develop a vacuum in the container. Non-collapsible or rigidsealed containers have the disadvantage of requiring various one-wayvalve mechanisms to permit air to enter the containers under vacuum toequalize the pressure in the containers with atmospheric pressure. Suchone-way valves typically suffer the disadvantage that they maintain atleast some vacuum pressure differential in the container and with manyviscous soaps, the presence of even a slight vacuum can negativelyaffect dispensing.

The present inventor has also appreciated that known soap dispenserssuffer the disadvantage that they do not permit for positive replacementof air for liquid dispensed from a liquid reservoir and/or do not permita positive pressure to develop in a container.

SUMMARY OF THE INVENTION

To at least partially overcome these disadvantages of previously knowndevices, the present invention provides a pump for dispensing fluidwhich provides for a positive replacement of liquid dispensed from acontainer, preferably with atmospheric air. The present invention alsoprovides a pump for dispensing liquid in the form of a foam preferablywithout creating a vacuum in a non-collapsible or rigid sealedcontainer.

An object of the present invention is to provide an improved pump fordispensing a liquid.

Another object is to provide an improved pump for dispensing a liquid inthe form of a foam.

Another object is to provide a pump for dispensing liquid from anon-collapsible or rigid sealed container without creating a vacuum inthe container.

Another object is to provide a pump which provides for positivereplacement of liquid dispensed from a container by atmospheric air.

Accordingly, in one aspect, the present invention provides a pump fordispensing liquid from a reservoir comprising:

-   -   a piston chamber-forming member having an inner cylindrical        chamber and an outer cylindrical chamber each having a diameter,        a chamber wall, an inner end and an outer end;    -   the diameter of the inner chamber being less than the diameter        of the outer chamber,    -   the inner chamber and outer chamber being coaxial with the outer        end of the inner chamber opening into the outer chamber;    -   an inner end of the inner chamber in fluid communication with        the reservoir;    -   a piston-forming element received in the piston chamber-forming        member axially slidable inwardly and outwardly therein between        an outward extended position and an inward retracted position;    -   the piston-forming element having an axially extending hollow        stem having a central passageway closed at an inner end and        having an outlet proximate an outer end;    -   an inner disk on the stem extending radially outwardly from the        stem adapted to engage to the chamber wall of the inner chamber;    -   an intermediate disk on the stem extending radially outwardly        from the stem adapted to engage the chamber wall of the inner        chamber, the intermediate disk spaced axially outwardly from the        inner disk relative the inner end of the stem;    -   an outer disk on the stem spaced axially outwardly from the        intermediate disk and extending radially outwardly from the stem        into engagement with the chamber wall of the outer chamber to        prevent fluid flow outwardly therebetween;    -   an inlet located on the stem between the outer disk and the        intermediate disk in communication with the passageway;    -   in the retracted position, the intermediate disk is received in        the inner chamber to prevent fluid flow from the outer end of        the inner chamber outwardly therepast and the inner disk does        not prevent fluid flow between the reservoir and the inner        chamber therepast via the inner end of the inner chamber;    -   in the extended position, the inner disk is received in the        inner chamber to prevent fluid flow from the inner end of the        inner chamber inwardly therepast and the intermediate disk does        not prevent fluid flow between the inner chamber and the outer        chamber via the outer end of the inner chamber.

Preferably, the pump includes a porous member in the passageway betweenthe inlet and the outlet for generating turbulence in fluid passingtherethrough to generate foam when air and liquid pass therethroughsimultaneously.

In preferred embodiments, the pump assembly provides for directreplacement of volumes of liquid from a reservoir with equal volumes ofair preferably at substantially atmospheric pressure, the same pressureor with pressure equalization to be at least equal to atmosphericpressure. A slide arrangement preferably positively displaces liquidfrom the reservoir and air into the reservoir. The pump draws air fromthe atmosphere into a chamber from which the air either is available forpassage to replace liquid from the reservoir or is pressurized to assistdispensing liquid, preferably, admixing with the liquid to providefoaming. Gravity separation of air and liquid to be dispensed is used toreplace liquid with air in the reservoir and to selectively place airand liquid into communication with passageways for ejection.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects and advantages of the present invention will becomeapparent from the following description taken together with theaccompanying drawings in which:

FIG. 1 is a partially cut-away side view of a first preferred embodimentof a liquid dispenser with a reservoir and pump assembly in accordancewith the present invention;

FIG. 2 is a partially exploded perspective view of the pump assemblyshown in FIG. 1;

FIG. 3 is a cross-sectional side view of an assembled pump assembly ofFIG. 2 showing the piston in a fully extended position;

FIG. 4 is the same side view as in FIG. 3;

FIG. 5 is a cross-sectional side view similar to FIG. 3 but with thepiston in an intermediate position in a retraction stroke;

FIG. 6 is a cross-sectional side view similar to FIG. 3 but with thepiston in a fully retracted position;

FIG. 7 is a cross-sectional side view substantially identical to FIG. 5with the piston in an intermediate position, however, in a extensionstroke;

FIG. 8 is a cross-sectional side view substantially identical to thatshown in FIG. 3, however, at the end of an extension stroke;

FIG. 9 is a cross-sectional side view of a pump assembly in accordancewith a second embodiment of the present invention;

FIGS. 10 and 11 are cross-sectional side views of the body and piston,respectively, of the pump assembly of FIG. 9;

FIG. 12 is a cross-sectional side view of the pump of FIG. 8 in a fullyextended position;

FIG. 13 is a cross-sectional side view of the pump assembly of FIG. 8 inan intermediate position;

FIG. 14 is a cross-sectional side view of the pump assembly of FIG. 8 ina fully retracted position;

FIG. 15 is a cross-sectional side view of a piston for a pump assemblyin accordance with a third embodiment of the present invention;

FIG. 16 is a cross-sectional side view of a piston for a pump assemblyin accordance with a fourth embodiment of the present invention;

FIG. 17 is a cross-sectional side view of a pump assembly in accordancewith a fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Reference is made first to FIGS. 2 and 3 which show a pump assemblygenerally indicated 10. Pump assembly 10 is best shown in FIG. 2 ascomprising two principal elements, a piston chamber-forming body 12 anda piston 14.

Referring to FIG. 3, body 12 has an inner cylindrical chamber 18 and anouter cylindrical chamber 20 both coaxially disposed about an axis 22.The inner chamber 18 has an inlet opening 24 and an outlet opening 26.The inner chamber has a cylindrical chamber side wall 28. The outletopening 26 opens into an inlet end of the outer chamber 20 from anopening in a shoulder 32 forming the inner end of the outer chamber 20.The outer chamber has an outlet opening 34 and a cylindrical chamberside wall 36.

Piston 14 is axially slidably received in the body 12. The piston 14 hasan elongate stem 38 upon which four disks are provided at axially spacedlocations. An inner sealing disk 40 is provided at an innermost endspaced axially from an intermediate sealing disk 42 which, in turn, isspaced axially from an outer sealing disk 44. The inner sealing disk 40and intermediate sealing disk 42 are adapted to be axially slidablewithin the inner chamber 18. Each of the inner sealing disk 40 andintermediate sealing disk 42 extend radially outwardly from the stem 38so as to be adapted to sealably engage the side wall 28 of the innerchamber 18.

The outer sealing disk 44 is adapted to be axially slidable within theouter cylindrical chamber 20. The outer sealing disk 44 extends radiallyoutwardly from the stem 38 to sealably engage the side wall 36 of theouter chamber 20.

The piston 14 essentially forms, as defined between the inner sealingdisk 40 and the intermediate sealing disk 42, an annular innercompartment 64 which opens radially outwardly as an annular openingbetween the disks 42 and 44. Similarly, the piston 14 effectively formsbetween the intermediate sealing disk 42 and the outer sealing disk 44an annular outer compartment 66 which opens radially outwardly as anannular opening between the disks 42 and 44.

An outermost portion of the stem 38 is hollow with a central passageway46 extending from an outlet 48 at the outermost end 50 of the stem 38centrally through the stem 38 to a closed inner end 52. Radiallyextending inlets 53 and 54 extend radially through the stem into thepassageway 46, with the inlets 53 and 54 being provided on the stem inbetween the outer sealing disk 44 and the intermediate sealing disk 42.A foam inducing screen 56 is provided in the passageway 46 intermediatebetween the inlets 53 and 54 and the outlet 48. The screen 56 may befabricated of plastic, wire or cloth material. It may comprise a porousceramic measure. The screen 56 provides small apertures through which anair and liquid mixture may be passed to aid foam production as byproduction of turbulent flow through small pores or apertures of thescreen thereof in a known manner.

The piston 14 also carries an engagement flange or disk 62 on the stemoutward from the outer sealing disk 44. Engagement disk 62 is providedfor engagement by an activating device in order to move the piston 14 inand out of the body 12.

Reference is now made to FIG. 1 which shows a liquid soap dispensergenerally indicated 70 utilizing the pump assembly 10 of FIGS. 2 and 3secured in the neck 58 of a sealed, non-compressible, rigid reservoir 60containing liquid hand soap 68 to be dispensed. Dispenser 70 has ahousing generally indicated 78 to receive and support the pump assembly10 and the reservoir 60. Housing 78 is shown with a back plate 80 formounting the housing, for example, to a building wall 82. A bottomsupport plate 84 extends forwardly from the back plate to support andreceive the reservoir 60 and pump assembly 10. As shown, bottom supportplate 84 has a circular opening 86 therethrough. The reservoir 60 sitssupported on shoulder 79 of the support plate 84 with the neck 58 of thereservoir 60 extending through opening 86 and secured in the opening asby a friction fit, clamping and the like. A cover member 85 is hinged toan upper forward extension 87 of the back plate 80 so as to permitreplacement of reservoir 60 and its pump assembly 10.

Support plate 84 carries at a forward portion thereof an actuating lever88 journalled for pivoting about a horizontal axis at 90. An upper endof the lever 88 carries a hook 94 to engage engagement disk 62 andcouple lever 88 to piston 14, such that movement of the lower handle end96 of lever 88 from the dashed line position to the solid line position,in the direction indicated by arrow 98 slides piston 14 inwardly in aretraction pumping stroke as indicated by arrow 100. On release of thelower handle end 96, spring 102 biases the upper portion of lever 88downwardly so that the lever draws piston 14 outwardly to a fullywithdrawn position as seen in dashed lines in FIG. 1. Lever 88 and itsinner hook 94 are adapted to permit manual coupling and uncoupling ofthe hook 94 as is necessary to remove and replace reservoir 60 and pumpassembly 10.

In use of the dispenser 70, once exhausted, the empty reservoir 60together with the attached pump 10 are removed and a new reservoir 60and attached pump 10 may be inserted into the housing. Preferably, theremoved reservoir 60 with its attached pump 10 are both made entirelyout of recyclable plastic material which can easily be recycled withoutthe need for disassembly prior to cutting and shredding.

FIG. 3 shows as dotted line 43 a preferred level of liquid in the outerchamber 20 ready for expulsion in a retraction stroke. Liquid level line43 is above inlet 54 but below inlet 53 so that air above line 43 is incommunications with inlet 53 and liquid is in communication with inlet54.

Reference is now made to FIGS. 4 to 8 which show a cycle of operation inwhich the piston 14 is moved in a retraction stroke from the extendedposition of FIG. 4 to the intermediate position of FIG. 5 and then tothe fully retracted position of FIG. 6. Subsequently, piston 14 is movedin an extension stroke from the fully retracted position of FIG. 6, tothe intermediate position of FIG. 7 and, subsequently, to the fullyextended position of FIG. 8. It is to be appreciated that FIGS. 5 and 7both show the piston 14 in the intermediate position and FIGS. 4 and 8both show the piston in the fully extended position. For convenience ineach of FIGS. 4 to 8, the engagement disk 62 is not shown.

In the fully extended position as seen in FIG. 4, the inner sealing disk40 closes the inner chamber 18 preventing flow inward and outwardthrough the inner chamber 18. The intermediate sealing disk 42 isdisposed in the outer chamber 20. With the intermediate sealing disk 42in the larger diameter outer chamber 20, the inner compartment 64 andouter compartment 66 are in communication with each other.

As seen in FIG. 4 and in every position which the piston 14 can assumein each of FIGS. 4 to 8, the outer sealing disk 44 engages the side wall36 of the outer chamber 20 and prevents liquid flow inwardly oroutwardly therepast. As well, at all times, the outlet 48 of the centralpassageway 46 is in communication with the outer compartment 66 via thepassageway 46 and inlets 53 and 54.

In the fully extended position shown in FIG. 4 with the inner chamber 18vertically above the outer chamber 20, to the extent there is any liquidin the inner compartment 64, that liquid will, under gravity, flow frominner compartment 64 downwardly into outer compartment 66 to be replacedby air in the outer compartment 66 rising upwardly into the innercompartment 64.

In moving from the fully extended position of FIG. 4 to the intermediateposition of FIG. 5, since the outer chamber 20 has a larger diameterthan the inner chamber 18, air and liquid in both the inner compartment64 and outer compartment 66 are compressed and forced to exit the outercompartment 66 via inlets 53 and 54 into the central passageway 46, downthe central passageway 46 through the wire screen 56 and, hence, downthe central passageway 46 to exit the outlet 48. The nature of theinlets 53 and 54 are to be chosen to enhance appropriate mixing of airand liquid in the passageway 46 prior to engaging the screen 56. Forexample, as shown, inlet 54 is larger than inlet 53. Larger inlet 54 isprovided closer to the outer sealing disk 44. Smaller inlet 53 isprovided at a height above the larger inlet 54 closer to theintermediate sealing disk 42. Since liquid will flow under gravity tolie on outer disc 44, larger inlet 54 is more likely to have liquidforced therethrough, whereas smaller inlet 53 is more likely to have airforced therethrough than larger inlet 54.

FIG. 5 shows an intermediate position in the retraction stroke beingillustrated as a point when each of the inner sealing disk 40 and theintermediate sealing disk 42 seal the inner chamber 18 with bothpreventing fluid flow therethrough. In the preferred illustratedembodiment, substantially simultaneously with the intermediate sealingdisk 42 commencing to close the inner chamber 18, the inner sealing disk40 becomes moved inwardly from the inner chamber 18 to open the innercompartment 64 to the reservoir 60.

In moving from the position of FIG. 4 to the position of FIG. 5, airwithin the inner compartment 64 moves upwardly into the inner chamber18. In moving from the position of FIG. 4 to the position of FIG. 5, itis to be appreciated that the inner chamber 18 is continuously sealedagainst flow therethrough by the inner sealing disk 40. In moving fromthe intermediate position of FIG. 5 to the fully retracted position ofFIG. 6, it is to be appreciated that the intermediate sealing disk 42continuously forms a seal with the inner chamber 18 preventing fluidflow therethrough. Once the intermediate sealing disk 42 engages in theinner chamber 18 as seen in FIG. 5, then the inner compartment 64 is nolonger in communication with the outer compartment 66. As well, once theinner sealing disk 40 is located inwardly from the inner chamber 18 sothat it no longer seals the inner chamber 18, then the inner compartment64 is in communication with the interior of the reservoir 60.

Air which is within the inner compartment 64 in the intermediateposition shown in FIG. 5, on inward movement of the piston 14 in theretraction stroke toward the position of FIG. 6, comes to be incommunication with the interior of the reservoir 60 and such air will,under gravity, float upwardly in the fluid 68 in the reservoir 60 and bedisplaced by liquid 68 from the reservoir 60 which will flow into theinner compartment 64. Thus, once the piston 14 moves inwardly from theintermediate position shown in FIG. 5 with the inner sealing disk 40 nolonger closing the inlet opening 26 of the inner chamber 18, then air inthe inner compartment 64 rises upwardly into the reservoir and fluid 68from the reservoir 60 fills the inner compartment 64.

On the piston reaching the intermediate position shown in FIG. 5, theintermediate sealing disk 42 forms a seal with the inner chamber 18 andthe outer compartment 66 is thereby isolated from the inner compartment64. Air and liquid in the inner compartment 66 is, on continued movementof the piston 14 from the position of FIG. 5 to the fully retractedposition of FIG. 6, continued to be compressed with air and liquid to bedisplaced out the inlets 53 and 54.

As seen in FIG. 6 in the fully retracted position, the outer sealingdisk 44 may engage the shoulder 32 forming the inlet end of the outerchamber 20.

An extension cycle is now discussed referring to the movement of thepiston from the position of FIG. 6 to the position of FIG. 8.

In the position of FIG. 6, only a small residual amount of liquid willremain within the outer compartment 66. On moving of the piston 14 fromthe position of FIG. 6 to the position of FIG. 7, liquid which fills theinner compartment 64 is moved downwardly into the inner chamber 18 andbecomes captured between the inner sealing disk 40 and intermediatesealing disk 42 within the inner chamber 18 once the inner sealing disc40 enters the inner chamber 18. Meanwhile, since the diameter of theinner chamber 18 is less than the diameter of the outer chamber 20, apartial vacuum is created within the outer compartment 66 which drawsair inwardly via the outlet 48, through the screen 56 and passageway 46and the inlets 53 and 54 into the outer compartment 66.

From the intermediate position shown in FIG. 7, on movement of thepiston 14 outwardly towards the fully extended position of FIG. 8, theinner sealing disk 40 seals the inner chamber 18 against flowtherethrough and the intermediate sealing disk 42 moves inwardly beyondthe inner chamber 18 so as to provide communication between the innercompartment 64 and the outer compartment 66. Once communication isestablished between the inner compartment 64 and the outer compartment66, liquid in the inner compartment 64 flows under gravity down into theouter compartment 66 and air in the outer compartment 66 flows upwardlyinto the inner compartment 64. With the further downward movement of thepiston 14 to the fully extended position of FIG. 8, air continues to bedrawn into the combined inner compartment 64 and outer compartment 66via the outlet 48, passageway 46 and inlets 53 and 54 such that onreaching the fully extended position, as seen in FIG. 8, liquid in theouter compartment 66 will form a layer upon the outer sealing disk 44.FIG. 8 is identical to FIG. 4 and the pump cycle may be repeated.

It is to be appreciated that the relative volume of the innercompartment 64 and outer compartment 66 may be chosen so as to have adesired proportion of liquid and air in the combined inner compartment64 and outer compartment 66 in the fully extended position and,preferably, with volume of liquid such that a level of liquid in thecompartment 66 below the inlet 53 but above the inlet 54.

The fact that in the first embodiment air is drawn upwardly through theoutlet 48 can be of assistance in reducing dripping of foam and liquidand, as well, can be of assistance in ensuring a mixture of liquid andfoam in the passageway 46 above the screen 56 in a subsequent retractionstroke when liquid and air are to be dispensed.

The relative amounts of air and liquid in the compartments 64 and 66 inthe fully extended position as well as the manner and nature of theinlets 53 and 54 can be significant as, for example, to determine theextent to which air may be compressed in the outer chamber 20 which canhave an effect on the velocity of air flowing through the screen 56 and,hence, the extent to which foaming may be accomplished.

The preferred embodiment illustrated in FIGS. 2 to 8 shows the innersealing disk 40 and intermediate sealing disk 42 in the intermediateposition both sealing the inner chamber 18. It is to be appreciated thatunder one preferred arrangement, preferably, at least one of the innersealing disk 40 and intermediate sealing disk 42 seals the inner chamber18 at all times. It is to be appreciated, however, that it is possibleto have the inner sealing disk 40 and intermediate sealing disk 42spaced axially a distance such that there is a time during movementbetween the fully extended position and the fully retracted position inwhich neither of the inner sealing disk 40 and intermediate sealing disk42 seal the inner chamber 18 and this can be advantageous, for example,to permit increased quantities of air to move upwardly into thereservoir while additional quantities of liquid move downwardly out ofthe reservoir.

Having the condition arise that neither the inner sealing disk 40 northe intermediate sealing disk 42 seal the inner chamber 18 for at leasta small portion of the stroke can be advantageous to permit equalizationof the pressures in the reservoir and in the outer compartment 66 as maybe useful, for example, to assist in ensuring that a vacuum does notarise in the interior of the reservoir and/or to reduce the likelihoodof preventing an unduly large positive pressure from being developedwithin the reservoir.

The pump could alternatively be structured so as to provide with eachstroke a small amount of air under pressure into the interior of thereservoir, which positive pressure, provided it is not dangerous to theintegrity of the container, can assist in urging liquid to exit thereservoir into the inner chamber 18 when the inner sealing disc 40 isnot sealing entry into the inner chamber 18.

The length of the stroke of the piston as, for example, from theintermediate position to the fully extended position can be varied so asto control the amount of air which is drawn into the outer chamber 20.The length of the stroke by which the piston 14 is moved from theintermediate position to the fully retracted position can be varied tocontrol the extent to which liquid and air may be expelled in anystroke.

Reference is now made to FIGS. 9 to 14 which illustrate a secondembodiment of a pump assembly in accordance with the present invention.Throughout the drawings, the same reference numerals are used to referto like elements.

FIG. 9 also shows a pump assembly 10 having a piston chamber-formingbody 12 and a piston 14. The piston chamber-forming body 12 isthreadably secured to the neck 58 of a rigid sealed bottle 60. Body 12is provided with an axially extending generally cylindrical rim 102provided outwardly from the outer chamber 20 and carrying inwardlydirected threads 104 adapted to engage complementary threads 106 carriedon the neck 58 of the bottle 60.

FIG. 9 also shows a removable cover 107 which fits in a snap-fitengagement onto body 12 forming an airtight annular seal thereabout toprotect the pump assembly 10 from contamination prior to use as, forexample, during shipment. As best seen in FIG. 10, the body 12 is formedwith a cylindrical outer tubular portion 108 connected at an inner endvia a radially extending flange portion 110 to a cylindrical innertubular portion 112. The inner tubular portion 112 extends axiallyradially inside the outer tubular portion 108.

The outer chamber 20 is formed radially inwardly of the outer tubularportion 108 having a side wall 36 thereabout and open at its outletopening 34. As shown, the side wall 36 tapers outwardly at chamfers 35proximate the outlet opening 34 to facilitate entry of the piston 14.

An inner chamber 18 is formed radially inwardly of the inner tubularportion 112. The inner tubular portion 112 defines an outlet opening 26of the inner chamber 18 and a side wall 28 thereof. The inner chamber 18has its side wall 28 taper outwardly as a chamfer 25 proximate theoutlet opening 26 to facilitate entry of the piston into the innerchamber 18. The side wall 28 has a portion 27 of constant diameterbetween chamfer 25 and an axially inwardly spaced chamfer 29. The sidewall 28 of the inner chamber 18 has a portion 31 of increased diameterrelative to the constant diameter portion 27 spaced axially inwardlyfrom the constant diameter portion 27 by chamfer 29. The increaseddiameter portion 31 permits fluid flow inwardly and outwardly in theinner chamber 18 past the inner disk 40 of the piston 14 when the piston14 is in the fully withdrawn position as seen in FIGS. 9 and 14.

The inner tubular portion 112, outer tubular portion 108, inner chamber18 and outer chamber 20 are each coaxial about axis 22.

The inner tubular portion 112 extends axially inwardly from flangeportion 110 as a series of circumferentially spaced arms 114, only oneof which is shown cross-sectioned on the left-hand side of FIGS. 9, 10and 12 to 14 to support an annular ring 116 disposed coaxially about thecentral axis 22. The ring 116 serves as a guide to assist in guiding acylindrical inward guiding portion 118 of a stem 38 of the piston 14 incoaxial sliding within the body 12. Spaces 119 are provided between thearms 114 as shown on the right-hand side of FIGS. 9, 10 and 12 to 14 toprovide free communication for fluid between the reservoir and theinterior of the inner tubular portion 112, radially through the tubularportion 112.

As best seen in FIG. 11, the piston 14 is formed from six elements,namely, an outer casing 120, an inner core 122, a center plug 124, aspacer ring 126 and two screens 56 and 57.

The outer casing 120 is of enlarged diameter at its axially inner endwhere the outer disk 44 is provided. The outer disk 44 is shown asincluding a locating flange 128 to locatably engage the cylindrical sidewall 36 of the outer chamber 20 and a resilient flexible circularsealing disk 130 which sealably engages the side wall 36 and preventsflow of fluids axially outwardly therepast.

The outer casing 120 is shown with the outer disk 44 carried as aradially outwardly extending flange on a cylindrical large tube portion132 which extends axially outwardly to a radially inwardly extendingshoulder 134 supporting a small tube portion 136 extending axiallyoutwardly from the shoulder 134 to the outlet 48. Outer screen 57 islocated on the shoulder 134. Outer screen 57 is held on the shoulder 134by the annular spacer ring 126 spaced outward of an inner screen 56. Theinner core 122 sandwiches the outer screen 57 onto the ring 126. Theinner core 122 also carries the plug 124 coaxially extending inwardlyinto the inner core 122 inwardly of the outer screen 57.

The inner core 122 carries the inner disk 40 and the intermediate disk42. Each of the inner disk 40 and intermediate disk 42 comprise circularresilient flexible disks each of which extends radially outwardly andaway from the outlet 48. Each of the inner flexible 40 and intermediateflexible disk 42, when engaged with the constant diameter portion 27 ofthe inner chamber 18, prevent fluid flow axially outwardly therepastthrough the inner chamber 18, however, are adapted to have theirresilient outer edges deflect radially inwardly to permit fluid flow,under pressure differentials above a predetermined pressure, axiallyinwardly past the disks.

As seen in FIGS. 9 and 12, when the inner disk 40 is located in theinner chamber 18 inwardly from the constant diameter portion 27 in theincreased diameter portion 31, then the inner disk 40 does not preventflow of fluid between the inner chamber 18 and the reservoir 60.

The inner core 122 has a hollow bore 140 closed at an axial inner end at142 and open at an axial outer end. The plug 124 is coaxially receivedwithin the bore 140 at the axial outer end. The plug 124 has an elongatebody 143 which extends inwardly into the bore 140. The plug 124 has aradially extending base 144 at its outer end with a plurality ofcircumferentially spaced opening 146 therethrough. The body 143 of theplug 124 carries an integral central sealing disk 148 which extendsradially outwardly from the body 143 to engage the side wall of the bore140. The central sealing disk 148 has a deformable edge portion whichengages the side wall of the bore 140 to prevent fluid flow axiallyinwardly therepast in the bore, however, permits fluid flow outwardlytherepast under pressures above a predetermined pressure necessary todeflect the central sealing disk 148 out from engagement with the sidewall of the bore.

The inner core 122 includes a cylindrical lower portion 123 which has aplurality of flutes at circumferentially spaced locations thereaboutwhich effectively form with the outer casing 120 peripheral passageways152 which extend axially. Passageways 152 are open to the outercompartment 66 between disks 42 and 44 at openings 150 at the inner endsof the passageways. At the outer ends, the passageways 152 join radialinlets 54 in the lower portion 123 which provide communication into thecentral bore 140.

Radially extending inlet 53 extends into the bore 140 from the outercompartment 66 between the intermediate disk 42 and the outer disk 44.

The piston 14 provides a common flow path which is provided for flow offluids in the bore 140 immediately inwardly above the base 144 of theplug 124, through the openings 146 in the base 144 of the plug 124,through the inner screen 57, through a hollow central opening 127 in thespacer ring 126, through the outer screen 56 and, hence, through thesmaller tube portion 136 to the outlet 48. However, the piston 14provides two different pathways for flow of fluid from the outercompartment 66 to the openings 146 in the base 144 of the plug 124.

A first pathway permits flow via openings 152, peripheral passageways150 and inlets 54 into the bore 140. The first pathway permits fluidflow both inwardly and outwardly and is particularly adapted to receiveany liquid which under gravity flows down to the lower and axiallyoutermost portion of the outer compartment 66 where the openings 150 tothe peripheral passageways 150 are provided.

A second pathway provides flow via the inlet 53 into the bore 140 andpast the central sealing disk 148 to the openings 146 in the base 144 ofthe plug 124. It is to be appreciated that this second pathway is onlyopen to fluid flow outwardly from the outer compartment 66 since thecentral sealing disk 148 prevents fluid flow inwardly therepast.Preferably, as shown, the inlets 53 are disposed at an axial innerlocation in the outer compartment 66 so as to be more likely to have theinlet 53 receive air which will rise to the upper and axial inner end ofthe upper compartment 64 underneath the intermediate disk 42 and befound above a level of liquid in the lower outer compartment 66.

Operation of the second embodiment of FIGS. 9 to 14 is similar to thatwith the first embodiment of FIGS. 1 to 8.

In a fully extended position as seen in FIG. 12, the inner sealing disk40 seals the inner chamber 18 against fluid flow outwardly therefrom. Inan intermediate position as shown in FIG. 13, both the inner disk 40 andthe intermediate disk 42 seal the inner chamber 18 against fluid flowoutwardly therethrough. In the fully retracted position as shown in FIG.14, the intermediate disk 42 seals the inner chamber 18 from fluid flowoutwardly from the reservoir.

In the fully extended position as seen in FIG. 12, the intermediate disk42 is withdrawn inwardly past the inner tubular portion 112 to aposition in which it does prevent flow of fluid between the innercompartment 64 and the outer compartment 66 and the two compartments arein communication.

In the fully retracted position as shown in FIG. 14, the inner disk 40does not prevent flow of fluid therepast and, hence, the reservoir 60 isin communication with the inner compartment 64.

In a retraction stroke, on moving from the position of FIG. 12 to theposition of FIG. 13, air and/or liquid is compressed and thereby forcedto pass outwardly from the outer compartment 66 via either the firstpathway through peripheral passageways 152 and inlet 54 or via thesecond pathway through the inlet 53 and past the central sealing disk148 in bore 140. The central sealing disk 148 provides resistance tofluid flow axially outwardly therepast. This is advantageous in asituation where liquid fills the lowermost portion of the outercompartment 66 such that liquid is being urged via the first pathwaythrough the peripheral passageways 152 and inlet 54 and air fills theupper portion of the outer chamber 66 such that air is being forced viathe second pathway through the inlet 53 and bore 140 onto the centralsealing disk 148. The central sealing disk 148 is preferably chosen soas to require a predetermined air pressure differential before air maybe permitted to flow outwardly therepast.

The resistance of liquid flowing from the peripheral passageways 152,inlet 54, openings 146 in the plug 124 and through the screens 56 and 57requires a pressure on the liquid sufficiently to force the liquidtherethrough. The central sealing disk 148 is preferably selected sothat air pressurized to a pressure at least equal to that required toovercome the resistance to liquid flow will be required for air flowpast the central sealing disk 148. Providing the air to be pressurizedto pass by the central sealing disk 148 is of assistance in providingfor turbulent air flow through the screens 56 and 57 which, when liquidhas also been passed through the screens, provides for preferred foamingas liquid and air are passed effectively simultaneously through thescreens.

In an extension stroke on moving from the position of FIG. 13 to theposition of FIG. 14, air is drawn into the outer compartment 66. Onepathway for the air to be drawn in is via the outlet 48, through thescreens 56 and 57 and, hence, via the inlet 54 and peripheralpassageways 152 into the outer compartment 66. Air cannot be drawninwardly through the bore 140 and inlet 53 since the bore 120 is blockedagainst flow inwardly therepast by the central sealing disk 148.

As shown in FIG. 12, the outer disk 44 includes a resilient sealing disk130 which is formed as a thin resilient disk having an elasticallydeformable edge portion near the side wall 36 of the outer chamber 20.This edge portion of the sealing disk 130 is deflectable radiallyinwardly so as to permit, under a sufficiently high vacuum differential,air to flow axially inwardly therepast. Preferably, the piston 14 may beconfigured such that substantially all air to be drawn inwardly is drawninwardly via the peripheral passageways 146 and the first pathway,however, a device could be arranged such that the restriction to flowthrough the first pathway, and/or the screens 57 and 56 is such thatsome proportion or substantially all the air is drawn past the sealingdisk 130. The locating flange 128 on the outer disk 44 is preferablyprovided to permit fluid flow therepast but could be configured toprevent fluid flow inwardly and/or outwardly.

In a withdrawal stroke, to the extent that a vacuum may come to bedeveloped in the inner compartment 64 and/or in the reservoir 60, thisvacuum can be relieved by reason of fluid flow inwardly past each of theinner disk 40 and intermediate disk 42. It is to be appreciated,however, that the development of a continuous vacuum within thereservoir 60 in preferred operation of the pump assembly 10 should beavoided, however, a temporary vacuum can assist in drawing air upwardlyfrom the inner compartment 64.

Reference is made to FIG. 15 which shows a piston 14 for a pump assemblyin accordance with a third embodiment of the present invention. Thepiston 14 of FIG. 15 is identical to the piston 14 of FIG. 11 with theexception that the inlet 53 of FIG. 11 has been eliminated and thecenter plug 124 of FIG. 11 has been replaced with a modified center plug156.

Center plug 156 of FIG. 15 comprises a hollow tubular member 158 with awidened base 144. The tubular member 158 has a bore 160 extendingcentrally therethrough from an open inner opening 162 to an open outeropening 164.

The tubular member 158 is disposed coaxially in bore 140 so as toprovide an annular passageway 166 annularly about the tubular member158.

The embodiment of FIG. 15 provides a single pathway for fluid flowbetween the outer compartment 66 and the outlet 48 via passageways 152,inlet 154, annular passageway 166, bore 160, screen 56, opening 127,screen 57 and bore 140.

This pathway can be selected to have a relative length and relativecross-section which resists flow of fluid inwardly and outwardlytherethrough and, particularly, can assist in preventing liquid fromdripping out the outlet 48 as when the pump assembly is left inactiveas, for example, in positions similar to that of FIGS. 13 or 14.

The relative vertical height of the inner opening 162 to the tubularmember 158 relative the outer compartment 66 can determine the level ofliquid which will be maintained in the outer compartment 66 if theliquid is free to drip under gravity out of the outlet 48.

The relative volume of fluid which would be required to fill thecompartment 66, passageway 152, inlets 54 and passageway 166 to a heightof the inner opening 162 may advantageously be selected towardsassisting in gauging the volume of fluid to be held in the outercompartment 66. The embodiment of FIG. 15 can be used without screens 56and 57 when foaming is not desired.

Reference is made to FIG. 16 which shows a fourth embodiment of a piston14 in accordance with the present invention and which is identical tothe piston in FIG. 15 with the exception that the two screens 56 and 57and the ring 126 have been eliminated, the center plug 156 is ofincreased length and the bore 140 has been extended further inwardly.FIG. 16 illustrates a piston 14 for use to dispense liquid withoutfoaming. The inner opening 162 of the tubular member 158 is inward ofthe inner disk 40 to assist in preventing liquid in the outercompartment 66 from flowing due to gravity out the outlet 48. It is tobe appreciated that the relative location of the inner opening 162 canbe selected to be at any relative height from that of inlet 54 to aheight inward of the inner disk 40

To assist, or provide at least some foaming, an inlet similar to inlet53 in FIG. 9 could be provided from the outer compartment 66 to theannular passageway 166, preferably outwardly of, that is, below theinner opening 162. By providing such inlet 53 to be small in size so asto restrict air flow therethrough until air in outer compartment 66 maybe sufficiently pressurized, then pressurized air will be injected underpressure into liquid passing through the annular passageway 166. Otherembodiments are possible in which a one-way valve mechanism preventsflow back from the annular passageway 166 through such an inlet 53 asis, for example, accomplished with the central sealing disk 148 of theembodiment of FIG. 9.

Reference is made to FIG. 17 which illustrates a fifth embodiment of apump assembly 10 in accordance with the present invention in a fullyretracted position.

The body 12 in FIG. 17 is similar to that in FIGS. 9 to 14 but carrieson its flange portion 110 an inward axially extending generallycylindrical support tube 170 adapted to support an air chamber-formingmember 172. Member 172 has a cylindrical side wall 174 and is closed atits inner end by end wall 176. Openings such as 178 are provided alignedthrough both the wall 174 and the support tube 170 to providecommunication from the interior of the reservoir into the interior ofthe support tube and hence into the inner chamber 18 as indicated byarrow 179.

The piston 14 in FIG. 17 is similar to that of FIGS. 9 to 14 but carriesat its inner end an air pump disk 180 fixedly supported by a hollow necktube 182 being fixedly secured within a hollow support tube 118 of theinner core 122. The neck tube 182 is open at both ends.

The air pump disk 180 includes a locating flange 184 to locatably engagethe cylindrical side wall 174 and a resilient flexible circular sealingdisc 186 which sealably engages the side wall 174 and prevents flow offluids axially outwardly therepast. An air chamber 186 is definedbetween the air chamber-forming member 172 and the air pump disk 180which will increase and decrease in volume as the piston 14 is movedaxially in the body 12 between the extended and retracted positions. Theair chamber 186 is in communication with the bore 140 via the neck tube182.

In reciprocal sliding of the piston 14 from the retracted position shownin FIG. 17 towards an extended position, fluid, notably air from theoutlet 48 but also possibly liquid and/or foam in the bore 140, is drawnupwardly into the air chamber 186 at the same time as liquid, foamand/or air is drawn into the lower compartment 66. In sliding of thepiston 14 from the extended position to the retracted position, airand/or other foam or fluid in the air chamber 186 is pressurized andforced outwardly through the bore 140 through the screen 56. The airpump disk 180 provides for inhalation and expulsion of fluids, notablyair, in addition to the quantities of fluid inhaled and expulsed by theremainder of the pump assembly and, thus, the air pump disk 180increases the volume of air which is available to be forced through thescreens 56 and 57 to produce foam. The configuration shown has the airpump comprising the air chamber-forming member 172 and the air pump disk180 inward from the remainder of the pump assembly 10 and of a diameternot exceeding that of the outer tubular portion 108. This is anadvantageous configuration to provide additional air pumping capacitywith the same piston stroke in a device which can be inserted into themouth of a reservoir.

FIG. 17 shows in addition to the two screens 56 and 57 to produce foam,a three dimensional basket-like screen 188 having generallyfrustoconical walls with small openings therethrough as in the manner ofknown filter members.

In FIG. 17, only one passageway 152 and inlet 54 is shown to providecommunication from the outer compartment 66 to the bore 140.

It is to be appreciated that the nature of the liquid to be dispensedincluding its viscosity and flow characteristics will be important inorder for a person skilled in the art to make suitable selection of therelative sizes and dimensions and resistance to flow provided by thevarious passageways, inlets, outlets and screens and/or past the variousdisks including the central sealing disk 148. As well, the quantity ofliquid desired to be dispensed in each stroke will have a bearing on therelative proportion and sizing of the components including particularlythe inner compartment 64, outer compartment 66 and the axial length of astroke of the piston.

In the preferred embodiments, the engagement disk 62 is provided on thepiston 14 for engagement to move the piston inwardly and outwardly. Itis to be appreciated that various other mechanisms can be provided forengagement and movement of the piston relative the body 12.

The preferred embodiments show dispensers for passing liquid and airthrough screens 56 and 57 to dispense the liquid as a foam. The screens56 and 57 can be eliminated in which case the dispensers illustratedcould serve to dispense liquid without foaming yet to deliver quantitiesof air to the reservoir and, in the context of a reservoir which is asealed rigid container, prevent the build up of a vacuum in thecontainer.

The preferred embodiments of the invention show passages for dispensingof the air and/or liquid as being provided internally within a piston.Such an arrangement is believed preferred from the point of view of easeof construction of the pump assembly 10. However, it is to beappreciated that passageways for dispensing the liquid and/or foam maybe provided, at least partially, as part of the body 12 or removablymounted to the body 12.

In accordance with the preferred embodiment illustrated, the relativebuoyancy of air within the liquid and, hence, the separation of air andliquid due to gravity are utilized as, for example, to permit air in thecompartment 64 to flow upwardly into the reservoir 60 and liquid in thereservoir 60 to flow downwardly into the inner compartment 64 as, forexample, when the inner compartment 64 is open to the reservoir. It isto be appreciated, therefore, that the pump assembly in accordance withthe presence invention should typically be disposed with what has beenreferred to as the inner end of the pump assembly at a height above theheight of the outer outlet end.

While this invention has been described with reference to preferredembodiments, the invention is not so limited. Many modifications andvariations will now occur to persons skilled in the art. For adefinition of the invention, reference is made to the appended claims.

1. A pump for dispensing liquid from a reservoir comprising: a pistonchamber-forming member having an inner chamber and an outer chamber eachhaving a chamber wall, an inner end and an outer end; the crosssectional area of the inner chamber being less than the cross sectionalarea of the outer chamber, the inner chamber and outer chamber beingcoaxial with the outer end of the inner chamber opening into the outerchamber; an inner end of the inner chamber in fluid communication withthe reservoir; a piston-forming element received in the pistonchamber-forming member axially slidable inwardly and outwardly thereinbetween an outward extended position and an inward retracted position;the piston-forming element having an axially extending hollow stemhaving a central passageway having an outlet proximate an outer end; aninner disk on the stem extending radially outwardly from the stemadapted to engage to the chamber wall of the inner chamber; anintermediate disk on the stem extending radially outwardly from the stemadapted to engage the chamber wall of the inner chamber, theintermediate disk spaced axially outwardly from the inner disk relativethe inner end of the stem; an outer disk on the stem spaced axiallyoutwardly from the intermediate disk and extending radially outwardlyfrom the stem into engagement with the chamber wall of the outer chamberto prevent fluid flow outwardly therebetween; a first inlet located onthe stem between the outer disk and the intermediate disk incommunication with the passageway; in the retracted position, theintermediate disk is received in the inner chamber to prevent fluid flowfrom the outer end of the inner chamber outwardly therepast and theinner disk does not prevent fluid flow between the reservoir and theinner chamber therepast via the inner end of the inner chamber; in theextended position, the inner disk is received in the inner chamber toprevent fluid flow from the inner end of the inner chamber inwardlytherepast and the intermediate disk does not prevent fluid flow betweenthe inner chamber and the outer chamber via the outer end of the innerchamber.
 2. A pump as claimed in claim 1 wherein: on axial movement ofthe piston-forming element from the retracted position to the extendedposition: (a) the intermediate disk moving from a blocking position inwhich it closes the outer end of the inner chamber from fluid flowtherepast to an open position in which it does not close the outer endof the inner chamber to free fluid flow therepast inwardly or outwardly,and (b) the inner disk moving from an open position in which it does notclose the inner end of the inner chamber to free fluid flow therethroughinwardly or outwardly to a blocking position in which it closes theinner end of the inner chamber from fluid flow therepast.
 3. A pump asclaimed in claim 2 wherein when the inner disk is in its blockingposition, the outer disk is in the open position and when the inner diskis in its open position, the outer disk is in its blocking position. 4.A pump as claimed in claim 2 wherein on axial movement of thepiston-forming element from the retracted position to the extendedposition air is drawn into the outer chamber from the outlet.
 5. A pumpas claimed in claim 1 including a porous member in the passagewaybetween the first inlet and the outlet for generating turbulence influid passing therethrough to generate foam when air and liquid passtherethrough simultaneously.
 6. A pump as claimed in claim 4 including aporous member in the passageway between the first inlet and the outletfor generating turbulence in fluid passing therethrough to generate foamwhen air and liquid pass therethrough simultaneously.
 7. A pump asclaimed in claim 1 in which each of the piston chamber-forming memberand piston-forming element is of generally circular cross-sectiondisposed coaxially about a central axis along which the piston-formingelement and piston chamber-forming member are slidable relative eachother.
 8. The pump as claimed in claim 1 in which the inner chamber isdisposed above the outer chamber with the inner end of the inner chamberabove the outer end of the inner chamber and the inner end of the outerchamber above the outer end of the outer chamber.
 9. A pump as claimedin claim 8 including a second inlet located on the stem between theouter disk and the intermediate disk in communication with thepassageway, the second inlet spaced on the stem spaced axially from thefirst inlet inwardly toward the inner disk.
 10. A pump assembly asclaimed in claim 9 including a one-way valve providing for fluid flowthrough the second inlet to the passageway but preventing fluid flowfrom the passageway through the second inlet.
 11. A pump as claimed inclaim 10 wherein the one-way valve prevents fluid flow through thesecond inlet to the passageway under a pressure differential across theone-way valve less than a selected pressure differential.
 12. A pump asclaimed in claim 5 in which the inner chamber is disposed above theouter chamber with the inner end of the inner chamber above the outerend of the inner chamber and the inner end of the outer chamber abovethe outer end of the outer chamber.
 13. A pump as claimed in claim 12including a second inlet located on the stem between the outer disk andthe intermediate disk in communication with the passageway, the secondinlet spaced on the stem spaced axially from the first inlet inwardlytoward the inner disk.
 14. A pump assembly as claimed in claim 10including a one-way valve disposed providing for fluid flow through thesecond inlet to the passageway but preventing fluid flow from thepassageway through the second inlet.
 15. A pump as claimed in claim 8wherein an outer compartment is defined by the piston-forming elementbetween the outer disk and the intermediate disk with an annular openingopen radially outwardly therebetween, an inner compartment is defined bythe piston-forming element between the intermediate disk and the innerdisk with an annular opening open radially outwardly therebetween,wherein in the retracted position, the inner compartment is incommunication with the reservoir via the annular opening of the innercompartment to permit air in the inner compartment to float upwardlyunder gravity into the reservoir from the inner compartment and bereplaced by liquid in the reservoir flowing downwardly into the innercompartment.
 16. A pump as claimed in claim 15 wherein in the extendedposition, the outer compartment and inner compartment are both incommunication with the outer chamber via their annular openings topermit air in the outer compartment to float upwardly under gravity intothe inner compartment and be replaced by liquid in the inner compartmentflowing downwardly into the outer compartment.
 17. A pump as claimed inclaim 16 including a porous member in the passageway between the firstinlet and the outlet for generating turbulence in fluid passingtherethrough to generate foam when air and liquid pass therethroughsimultaneously; including a second inlet located on the stem between theouter disk and the intermediate disk in communication with thepassageway, the second inlet spaced on the stem spaced axially from thefirst inlet inwardly toward the inner disk; wherein in a refractionstroke while expelling fluid from the outer compartment, the outercompartment contains a volume of liquid with air above a level of theliquid and the level of the liquid in the outer compartment drops tobecome below the second inlet before the level of the liquid drops to alevel of the first inlet.
 18. A pump as claimed in claim 1 wherein thepiston chamber-forming member having a cylindrical air pump chamberdisposed inwardly of the inner chamber coaxial therewith, the air pumpchamber having a diameter, a chamber wall, a closed inner end and anopen outer end, the stem of the piston-forming element extending axiallyinto the air pump chamber via the outer end of the air pump chamber, anair pump disk on the stem extending radially outwardly from the stem,the air pump disc received in the air pump chamber in all positions thepiston-forming element assumes in sliding between the extended positionand the retracted position with the air pump disc engaging the chamberwall of the air pump chamber to prevent fluid flow therepast inwardlyand outwardly; an inner end of the central passageway opening into theair pump chamber inwardly of the air pump disc; the air pump chamber andair pump disc form a variable volume closed compartment open only viathe inner end of the central passageway, with sliding of thepiston-forming element the relative movement of the air pump discchanging the volume of the closed compartment to draw fluid into theclosed compartment from the central passageway on sliding of thepiston-forming inwardly outwardly and to force fluid out of the closedcompartment via the central passageway on sliding of the piston-formingelement outwardly inwardly.
 19. A pump as claimed in claim 18 wherein:on axial movement of the piston-forming element from the retractedposition to the extended position: (a) the intermediate disk moving froma blocking position in which it closes the outer end of the innerchamber from fluid flow therepast to an open position in which it doesnot close the outer end of the inner chamber to free fluid flowtherepast inwardly or outwardly, and (b) the inner disk moving from anopen position in which it does not close the inner end of the innerchamber to free fluid flow therethrough inwardly or outwardly to ablocking position in which it closes the inner end of the inner chamberfrom fluid flow therepast.
 20. A pump as claimed in claim 19 whereinwhen the inner disk is in its blocking position, the outer disk is inthe open position and when the inner disk is in its open position, theouter disk is in its blocking position.
 21. A pump as claimed in claim20 wherein on axial movement of the piston-forming element from theretracted position to the extended position air is drawn into the outerchamber from the outlet.
 22. A pump as claimed in claim 18 including aporous member in the passageway between the first inlet and the outletfor generating turbulence in fluid passing therethrough to generate foamwhen air and liquid pass therethrough simultaneously.
 23. A pump asclaimed in claim 21 including a porous member in the passageway betweenthe first inlet and the outlet for generating turbulence in fluidpassing therethrough to generate foam when air and liquid passtherethrough simultaneously.
 24. A pump as claimed in claim 18 in whicheach of the piston chamber-forming member and piston-forming element isof generally circular cross-section disposed coaxially about a centralaxis along which the piston-forming element and piston chamber-formingmember are slidable relative each other.
 25. A pump as claimed in claim18 in which the inner chamber is disposed above the outer chamber withthe inner end of the inner chamber above the outer end of the innerchamber and the inner end of the outer chamber above the outer end ofthe outer chamber, and with the air pump chamber disposed above theinner chamber.
 26. A pump as claimed in claim 25 including a secondinlet located on the stem between the outer disk and the intermediatedisk in communication with the passageway, the second inlet spaced onthe stem spaced axially from the first inlet inwardly toward the innerdisk.
 27. A pump assembly as claimed in claim 26 including a one-wayvalve providing for fluid flow through the second inlet to thepassageway but preventing fluid flow from the passageway through thesecond inlet.
 28. A pump as claimed in claim 27 wherein the one-wayvalve prevents fluid flow through the second inlet to the passagewayunder a pressure differential across the one-way valve less than aselected pressure differential.
 29. A pump as claimed in claim 22 inwhich the inner chamber is disposed above the outer chamber with theinner end of the inner chamber above the outer end of the inner chamberand the inner end of the outer chamber above the outer end of the outerchamber.
 30. A pump as claimed in claim 29 including a second inletlocated on the stem between the outer disk and the intermediate disk incommunication with the passageway, the second inlet spaced on the stemspaced axially from the first inlet inwardly toward the inner disk. 31.A pump assembly as claimed in claim 26 including a one-way valveproviding for fluid flow through the second inlet to the passageway butpreventing fluid flow from the passageway through the second inlet. 32.A pump as claimed in claim 25 wherein an outer compartment is defined bythe piston-forming element between the outer disk and the intermediatedisk with an annular opening open radially outwardly therebetween, aninner compartment is defined by the piston-forming element between theintermediate disk and the inner disk with an annular opening openradially outwardly therebetween, wherein in the refracted position, theinner compartment is in communication with the reservoir via the annularopening of the inner compartment to permit air in the inner compartmentto float upwardly under gravity into the reservoir from the innercompartment and be replaced by liquid in the reservoir flowingdownwardly into the inner compartment.
 33. A pump as claimed in claim 32wherein in the extended position, the outer compartment and innercompartment are both in communication with the outer chamber via theirannular openings to permit air in the outer compartment to floatupwardly under gravity into the inner compartment and be replaced byliquid in the inner compartment flowing downwardly into the outercompartment.
 34. A pump as claimed in claim 33 including a porous memberin the passageway between the first inlet and the outlet for generatingturbulence in fluid passing therethrough to generate foam when air andliquid pass therethrough simultaneously; including a second inletlocated on the stem between the outer disk and the intermediate disk incommunication with the passageway, the second inlet spaced on the stemspaced axially from the first inlet inwardly toward the inner disk;wherein in a retraction stroke while expelling fluid from the outercompartment, the outer compartment contains a volume of liquid with airabove a level of the liquid and the level of the liquid in the outercompartment drops to become below the second inlet before the level ofthe liquid drops to a level of the first inlet.
 35. A pump as claimed inclaim 1 including an air pump mechanism comprising an air pump chamberand air pump disc slidable therein, one of the air pump chamber and airpump disc carried on the piston-chamber forming member and the othercarried on the piston-forming element, the air pump chamber and air pumpdisc interacting to form a variable volume compartment open to thecentral passageway to draw air into the closed compartment on movementof the piston-forming element inwardly outwardly and to force air out ofthe outlet on movement of the piston-forming element outwardly inwardly.